United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/094 Sept. 1985
&ER& Project Summary
Pilot Study for Removal of
Arsenic from Drinking
Water at the Fallon, Nevada,
Naval Air Station
Frederick Rubel, Jr., and Steven W. Hathaway
This report presents the pilot-plant
test results of two treatment methods
for removing arsenic from drinking
water—activated alumina and ion ex-
change. A mobile trailer was placed at a
site near the water distribution system
on the Fallen, Nevada, Naval Air Station
(NAS) grounds, where the arsenic con-
centration was measured at 0.080 to
0.116 mg/L. This level exceeded the U.S.
Environmental Protection Agency
(EPA) maximum contaminant level
(MCL) of 0.050 mg/L.
The trailer was equipped with three
PVC testing columns and an analytical
laboratory for the pilot project. The
NAS drinking water was used for evalu-
ating the efficacy of treatment under
several different conditions. The acti-
vated alumina and ion exchange sys-
tems were operated through three
loading and regeneration cycles each.
The major water quality factors affect-
ing the removal of arsenic by these
methods were pH of feed water, arsenic
concentration, suKate concentration,
and alkalinity. The major operational
factors affecting removal were flow
rate, down time, and media clogging.
The report also estimates the capital
and operating costs for arsenic removal
using the activated alumina method at
optimum pH (5.5) for each of the three
small community systems currently
using water from the same aquifer. The
pilot study estimated NAS capital costs
of $558,000 for a 1-mgd plant and oper-
ating costs of 220/1,000 gal of treated
water.
The project report also addressed
treatment and handling of the waste-
water generated by the arsenic removal
process, an issue often omitted from
treatabilrty studies. Several containers
of the regeneration waste were used
for a special study to characterize, de-
water, and render the waste nontoxic
for disposal in a sanitary landfill.
This project summary was developed
by EPA's Water Engineering Research
Laboratory, Cincinnati, OH, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information
at back).
Introduction
Many small communities are faced
with contamination of their ground-
water by inorganic chemicals. Arsenic
contamination can result from the
leaching of manmade toxic compounds
into the groundwater, or it can be
caused by the natural dissolution of
minerals from subterranean strata. Re-
gardless of the source of contamina-
tion, most small communities that have
drinking water with arsenic concentra-
tions higher than the U.S. Environmen-
tal Protection Agency (EPA) maximum
contaminant level (MCL) of 0.05 mg/L
do not have existing treatment facilities
that can be modified to reduce the ar-
senic to acceptable levels.
The arsenic concentration in the
Fallen, Nevada, Naval Air Station (NAS)
water supply was measured at 0.080 to
-------
0.016 mg/L, which exceeded the MCL of
0.050 mg/L established by EPA and the
Nevada State Health Division of the Bu-
reau of Consumer Health Protection
Services. A pilot plant study was, there-
fore, conducted to evaluate arsenic re-
moval from drinking water at the Fallon,
Nevada, Naval Air Station (NAS) using
activated alumina and ion exchange
technology. The primary objective of
the test project was to develop informa-
tion that would lead to the design and
economical installation of cost effective
treatment systems that could provide
potable water in compliance with the
MCL for arsenic.
Although the NAS, the City of Fallon,
and the Fallon Indian Reservation were
the primary recipients of this informa-
tion, the research data were developed
for use by other small communities in
determining cost effective treatment al-
ternatives for removing arsenic from
drinking water.
The work plan required a series of ar-
senic removal treatment tests. The stud-
ies included data acquisition and evalu-
ation of three separate treatment
modes using two different media. The
three treatment processes were as fol-
lows:
A. granular activated alumina with
pH adjustment (pH 5.5),
B. granular activated alumina with-
out pH adjustment, and
C. strong-base anion exchange resin
without pH adjustment.
Each treatment process was evalu-
ated through three complete treatment
cycles, with a cycle consisting of one
treatment run and one regeneration.
Additional tests were carried out to
study the effects of activated alumina
treatment at pH 6.0 and using upflow at
pH 5.5.
The treatment media used were
(1) Alcoa F-1* granular activated alu-
mina (28 to 48 mesh), and (2) Dow
Chemical Company Dowex SBR strong-
base anion resin (20 to 50 mesh).
Test Apparatus
The pilot plant apparatus consisted of
three separate systems—one for each
treatment mode and piped in parallel
(Figure 1). Each pilot treatment system
was designed to treat the well water at
a maximum flow rate of 1-1/2 gpm at
50 psi maximum working pressure. The
chlorinated well water was pumped to
the test site by NAS through a 1-in.,
"Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
PVC, schedule 80 pipe at an approxi-
mate pressure of 75 psig (the maximum
was 150 psig, and the minimum was
50 psig). The water flowed through a 5-
u,, powdered, activated carbon cartridge
filter for removal of chlorine, through a
pressure control valve, into a 1-in. man-
ifold. The manifold branched into three
separate systems, each with one 10-in.-
diameter by 60-in.-high treatment
column containing 1.0 ft3 of treatment
media.
The treatment columns had remov-
able heads on top and bottom. The
underdrain section occupied the bottom
6 in. of each column, and the treatment
media filled 22 in. The remaining height
was available for media expansion and
freeboard. The test apparatus was
piped for manual operation, with each
treatment system independent of the
other two.
The entire treatment system was
mounted in an insulated laboratory
trailer 30 ft long by 8 ft wide by 8 ft high.
In addition to the pilot plant equipment,
the trailer housed a chemical laboratory
that was equipped to perform all analy-
ses required during the duration of the
test program.
Pilot Test Program
The 1 ft3 of treatment media was
placed in each treatment vessel. The
volume was determined by weight,
using the manufacturer's published
data for material density (Alcoa F-1 52
Ib/ft3; Dowex SBR 44 Ib/ft3). Bed vol-
umes were also measured. The media
were carefully backwashed for removal
of fines.
The first cycle for each treatment
method was started at approximately
the same time. Initially, each mode
treated the water at the same flow rate,
1-1/2 gpm. This flow rate was estab-
lished as an optimum during previous
pilot test programs. Increasing the flow
rate may lower the removal efficiency;
decreasing the flow rate may or may not
increase efficiency, but it does extend
the test duration. This effect was moni-
tored closely during the testing. For
Column A, the treatment runs were ex-
tremely long and permitted iron de-
posits to build up in the media. This
buildup resulted in loss of treatment ef-
ficiency. Thus after 40 percent of the
first treatment run, the flow rate was
permanently decreased to 1 gpm. This
change alleviated the iron problem and
improved the treatment efficiency. The
runs for Columns B and C were very
short, and thus no flow rate adjust-
ments were considered for those
modes. After the initial startup, no at-
tempt was made to synchronize the be-
ginning or end of cycles of the different
treatment modes. Pilot test operation
for all practical purposes was continu-
ous; one cycle immediately followed
the completion of the previous cycle for
each treatment mode.
Raw and treated water samples for
each treatment mode were collected at
least once per day. During each regen-
eration, backwash and regeneration
wastewater grab samples were col-
lected at 5- and 10-min intervals. Grab
samples were also collected each time
the wastewater pH dropped 1 unit dur-
ing regenerations in which there was a
neutralization step. Composite samples
were taken during each step of regener-
ation. Analyses performed for raw,
treated, and regenerated water are
listed in Table 1. A complete raw water
analysis appears in Table 2. Since all
treatment methods were evaluated
using chlorinated feed water, the ar-
senic was assumed to be in the +5 va-
lence form. This assumption is based on
known arsenic water chemistry and is
supported by a recent investigation.
Each treatment method was operated
independently during testing. A de-
scription of the operation of each
method follows.
Method A. Activated Alumina
with pH Adjustment
The raw water was treated in a down-
flow, packed-bed configuration. The
flow rate was controlled initially at 1-1/2
gpm and then reduced to 1 gpm at 40
percent through the first run. Before en-
tering the treatment vessel, the raw
water was adjusted to pH 5.5 using a
dilute solution of sulfuric acid (H2SO4).
Each treatment run extended until the
arsenic level in the treated water was at
or very near the arsenic level in the raw
water. The treatment bed was then
backwashed with raw water, drained,
and regenerated in the upflow direction
with 4 to 4.5 percent NaOH solution. The
bed was then regenerated again in a
downflow direction. Upon completion
of the downflow regeneration, the bed
was flushed with raw water at a flow
rate of 1-1/2 gpm for 15 min.
At this point, the raw water pH was
adjusted to 2.5 and the neutralization
phase of the regeneration began. The
effluent pH was higher than 12 at the
beginning of this phase, and it dropped
slowly over an extended period. When
-------
IXJ
EH
-C
Legend
- Interface with Facility Piping
- Pressure Indicator
- Check Valve
- Ball Valve
- Hose Connection
Dilute HaSO
Day Tank
0-160 0-60
psig psig
O OP'
-vat-
Pressure
Carbon Reducing
Cartridge Va/ve
Filter
f Chlorine Kill)
4% NaOH 10%NaCR
Batch Batch
Tank Tank
1
o
0-60 psig
Turbine (~) p/
Meter V
m _ ?
r'\V2" f '-V'ifA
-T Rate of -*t- 5
f/oiv
Controller
Column 'A'
Granular
A ctivated A lumina
with pH A djustment
A cid Feed for Neutralization
.After Regeneration Q_^Q
I Turbine (~) PI
f Merer j =
M 8 U-V* ~l _ T S
^"/?ate/7ute /VaOW
Day Tank
^Sample
0-60 psig
Qpi 1
4 T Treated Effluent
Sample |^
3
-. Sample
0-60 psig
Op,
I Treated Effluent
4V" * l'/2
" Sample *YDr
3
-. Sample
O-60 psig
On
| Treated Effluent
3 A/"|^" 1 1 ^
Sample \Drain
J'/2"
Drain to Waste
Figure 1. Flow diagram for arsenic removal pilot plant.
the effluent pH reached 9.0, the influent-
adjusted pH was raised from 2.5 to 4.0,
at which point the next treatment run
began. When the effluent pH dropped to
6.5, the influent-adjusted pH was raised
from 4.0 to 5.5, where it remained
throughout the treatment run. The efflu-
ent pH was then adjusted to 7.5 with
dilute caustic. Because of the cost of
chemicals and because adding sodium
is not desirable, aeration was used to
raise the pH of the effluent for the re-
mainder of the study.
Method B. Activated Alumina
without pH Adjustment
This method was identical to Method
A except that pH was not adjusted dur-
ing the treatment run. The only pH
change occurred during the neutraliza-
tion step after regeneration.
Backwash and regeneration proce-
dures were also the same as for Method
A except that the acid feed adjusting the
pH to 2.5 was terminated when the ef-
fluent pH dropped to 9.0. The next treat-
ment run began then. The pH was not
adjusted further until the neutralization
phase of the next regeneration.
Method C. Strong Base Anion
Exchange Resin without pH
Adjustment
The raw water was treated in a
downflow, packed-bed configuration at
1-1/2 gpm. No pH adjustment was
made during the treatment or after
regeneration. Regeneration with 10%
-------
NaCI was used with the anion resin
followed by treated water rinse.
Results of Pilot Tests
Treatment Method A,
Activated Alumina with pH
Adjustment
The three test cycles of Method A ex-
periments were labeled A1, A2, and A3,
respectively. Each cycle ran for more
than 3 months before media exhaus-
tion.
Figure 2 presents loading curves for
the first run of each method tested (A, B,
and C). For cycle A1, arsenic was not
detectable in the effluent up to a treat-
ment volume of about 8,500 bed vol-
umes (BV) (63,000 gal). The effluent ar-
senic concentration reached the MCL of
(0.05 mg/L) at 15,536 BV (116,210 gal).
The media continued to remove arsenic
up to 24,500 BV (183,600 gal). At this
point, effluent arsenic concentration
reached 0.085 mg/L. The test run was
terminated because the activated alu-
mina capacity was nearly exhausted.
The arsenic removal capacity has
been calculated for all test runs (Table
3). In Test Run A1, the alumina removed
325 grains/ft3 (747 g/M3) of arsenic be-
fore any breakthrough occurred. The
test run was continued until the effluent
arsenic concentration reached the influ-
ent concentration. Total capacity calcu-
lated at this point was 655 grains/ft3
(1507 g/M3). Table 4 displays the test
data in terms of volume and run time.
The average amount of acid (66°B'
sulfuric acid) used to adjust raw water
to pH 5.5 during Method A testing was
0.130 gal/1000 gal of treated water.
During Test Run A1, the potential ex-
isted for blending 50 percent treated
water with 50 percent raw water and
still complying with the arsenic MCL.
Since the raw water arsenic level in later
treatment runs consistently exceeded
0.110 mg/L, a conservative design
would provide for blending 75 percent
treated water with 25 percent raw water.
Thus a water with 0.03 mg/L arsenic will
provide more flexibility in cases where
treatment conditions may change.
Table 5 analyzes the 75/25 blend for Run
A3 at 3,979 BV (29,760 gal).
Treatment Method B. Activated
Alumina with No pH
Adjustment
Column B contained 1 ft3 of F-1 Alcoa
activated alumina, as in Column A, and
operated at 1.5 gpm. The raw water pH
Table 1. Analytical Tests for Water Samples
Item
Daily Tests
Weekly Tests
Treatment Methods A & B
(activated alumina):
Raw and Treated Water
Regeneration Wastes
(samples taken at each re-
generation)
Treatment Method C
(anion exchange)
pH
Arsenic
Fluoride
Aluminum
Silica
Alkalinity
TDS
Arsenic
Aluminum
pH
Fluoride
Chloride
Sodium
pH
Arsenic
Alkalinity
TDS
Sulfate
Chloride
Fluoride
Total hardness
Carbonate
Bicarbonate
Sodium
Sulfate
Color
Calcium
Magnesium
Sulfate
TDS
Alkalinity
Total hardness
of 9.0 was not adjusted before treat-
ment in the three runs (B1, B2, B3). The
loading curve for Run B1 is compared
with those for A1 and C1 in Figure 2.
Test Runs B1, B2, and B3 were all
short cycles because of low removal ef-
ficiency. At pH 9.0 to 9.1, alumina is un-
favorable for arsenic removal but ideal
for silica removal. As expected, the ar-
senic removal performance was very
poor. Arsenic removal was complete
after only 3 days for Run B1, but Runs
B2 and B3 stopped removing arsenic af-
ter only 1 day. The raw water arsenic
level was 0.090 mg/L during the test pe-
riod. The treated water arsenic level was
as low as 0.008 mg/L. Because only one
Table 2. Fallon NAS Raw Water Analysis
water sample was collected per day,
there are very few data points. How-
ever, extrapolation of available data in-
dicates that during the run, 800 BV (5940
gal) were treated and 19 grains of ar-
senic were removed. Tables 3 and 4
summarize the results of the loading
curve. The treatment run was continued
until silica removal terminated.
For a short period after arsenic re-
moval ceased, a small amount of ar-
senic was desorbed from the bed. This
result indicates that at the higher treat-
ment pH, the alumina prefers silica to
arsenic. Some measurable fluoride re-
moval was also detected during the first
day of the run.
Analyte
Total alkalinity (as CaCo3)
Hardness (as CaCo3)
Calcium
Magnesium
Sodium
Aluminum
Chloride
Sulfate
Fluoride
Arsenic
TDS*
pH (units)
SiO2
Mean
246
5
1
1
240
0
101
96
0.788
0.103
535
9.1
28
Range
228-263
4-6
0-2
1
223-266
0
87-120
88-120
0.70-1.10
0.080-0.116
495-560
9.0-9. 1
28-34
"Values in mg/L except as noted.
f Total dissolved solids.
-------
Treatment Method C. Ion
Exchange
The results of the ion exchange tests
of Method C were similar to those of
alumina with no pH adjustment in
Method B. During the initial work with
the strong-base resin, it became imme-
diately obvious that sulfate was pre-
ferred to arsenic. Since the raw water
contained almost 100 mg/L sulfate and
less than 0.1 mg/L arsenic (ratio 1000:1),
the resin was expected to have nearly
zero capacity for arsenic. And because
sulfate is preferred, sulfate will displace
the arsenic after the arsenic break-
through point. Alkalinity was also re-
moved during the early part of the run
as shown by dropping pH; but later it
was also eluted from the bed by the sul-
fate. Figure 2 shows the loading curve
for Run C1 compared with those for B1
and A1. Only 300 to 500 BV (2244 to
3740 gal) could be treated before the
resin was exhausted for arsenic re-
moval. Tables 3 and 4 show the break-
through data points given for Runs C1,
C2, and C3.
Testing under Non-Optimum
Conditions
Because of the short test runs of alu-
mina at pH 9.0 (Runs B1, B2, and B3),
two tests were conducted to compare
the performance of an activated alu-
mina run at pH 6.0 with the test runs at
pH 5.5 (Runs A1, A2, and A3). Thus,
Column B was loaded with a fresh bed
of virgin activated alumina identical to
that used in Column A. If the tests were
successful, the benefits of operating at
pH 6.0 instead of pH 5.5 would include
the following:
1. Use of less acid for pH adjustment,
2. Higher pH of blended water, and
3. Lower treated water sulfate level.
The initial flow rate was 1.4 gpm in a
downflow configuration, similar to that
of Method A. After approximately 40
percent of the run, the flow rate was
reduced to 1.0 gpm.
Run B4 was terminated after treating
17,400 BV (130,000 gal) for a 29 percent
decrease in capacity from Run A1 at pH
5.5 (24,500 BV, or 183,260 gal). Figure 3
compares the results of Run B4 with
Run A3. No arsenic was detected in the
effluent until 7000 BV (52,360 gal) were
treated. A rather steady increase was
then detected up to about 12,000 BV
(89,760 gal). At 12,000, 15,000, 17,000
and 19,000 BV (89,760,112,220,127,160,
142,120 gal), the alumina bed seemed to
recover some capacity. This recovered
Table 3. Summary of Column Capacity
Arsenic Removal Capacity
Grains/ft3 (g/M3)
Test Run ID
A1 (Virgin)
A2
A3
B1 (Virgin)
B2
B3
C1 (Virgin)
C2
C3
B4 (Virgin)
B5
At First
Arsenic Detection
325 (747)
42 (95)
246 (566)
N.C."
2.6 (5.8)
2.6 (5.8)
N.C."
5.7 (13.0)
9.9 (22.4)
241 (554)
Df
At
Arsenic MCL
540 (1242)
490 (1107)
646 (I486)
18.3(42.1)
5.0(11.3)
3.2 (7.2)
N.C."
10.1 (22.8)
13.8 (31.2)
433 (979)
294 (676)
At
Media Exhaustion
655 (1507)
611 (1405)
730 (1679)
19.3 (44)
5.2(11.0)
3.7(8.5)
8.2 (18.5)
10.2 (23.)
13.9 (31.4)
536 (1233)
488 (1122)
"Samples not collected at low bed volume.
*D—All samples contained detectable arsenic.
Table 4. Summary of Treatment Volumes and Run Time
Volume Treated, galfbed volumes)
Test Run ID
A1
A2
A3
B1
B2
83
C1
C2
C3
B4
B5
At
First Arsenic
Detection
63,855 (8542)
8,270(1105)
39,890 (5332)
756 (101)
756 (101)
1,590 (212)
1,350 (180)
2,160(288)
35,550 (4752)
At
Arsenic MCL
116,210(15,536)
96,400 (12,888)
111,700(14,933)
5,940 (794)
1,260 (168)
2,160(288)
100,165(13,391)
57,560(7.695)
At
Media
Exhaustion
183,600 (24,545)
152,900 (20,447)
158,870 (21,239)
7,990 (794)
1,764 (235)
1,008 (134)
3,695 (493)
2,430 (324)
2,970 (397)
130,080 (17,390)
102,020 (13,639)
Run Time
(days)
111
105
110
4
1
1
1
1
1
94
67
Table 5. Analysis of Water from Run A3—Activated Alumina with Raw Water pH Ad-
justed to 5.5
Characteristic
P Alkalinity (as CaCO3)
M Alkalinity (as CaCO3)
Hardness (as CaCO3)
Calcium
Magnesium
Sodium
Aluminum
Chloride
Sulfate
Fluoride
Arsenic
Silica
TDS
pH (units)
Raw Water
(mg/L)'
50
246
5
0
1
240
0
101
96
0.80
0.110
28
535
9.1
Treated Water
(mg/L)"
0
30
5
0
1
240
.02
101
290
0.55
NDf
28
630
5.5
Aerated
Treated Water
(mg/L)"
0
30
5
0
1
240
.02
101
290
0.55
ND
28
630
7.5
Blend of 75%
Aerated Treated
Water with 25%
Raw Water
7
74
5
0
1
240
.02
101
230
0.65
0.028
28
600
8.6
"Except for pH.
tNot detectable.
-------
Q.12-\
0.10-
t
I o.os-
Ui
0.06-
0.04-
0.02-
0.00-
5000
~r
10000 15000
Bed Volumes
20000
25000
Figure 2. Loading curies for Run 1. methods (A.B.C).
capacity only occurred when the
column was shut off for a short period
of time. The data in Tables 3 and 4 show
the capacity of the alumina at various
points in the run. Before arsenic detec-
tion in the effluent, the alumina re-
moved 241 grains/ft3. At exhaustion, ar-
senic removal capacity for B4 was 536
grains/ft3 versus 655 grains/ft3 for Run
A1—an 18 percent reduction.
Before regeneration, the adjusted raw
water pH was lowered to 5.5 to deter-
mine whether any additional arsenic
could be removed by the alumina. The
results showed that an additional 26
grains of arsenic was removed from
2,580 BV (19,300 gal) at the lower pH.
Acid consumption for the reduction of
raw water pH to 6.0 was 0.107 gal 66°B'
sulfuric acid versus 0.130 gal for the pH
adjustment to 5.5 (17 percent reduc-
tion). Though this mode could reduce
acid consumption slightly and reduce
the sulfate concentration in the treated
water, these benefits were offset by
more frequent treatment-bed regenera-
tions. The latter liability more than off-
sets the benefits by increasing operat-
ing labor costs, generating more
wastewater, and producing higher
chemical costs for regeneration. Thus,
although operating with treatment pH
at 6.0 is technically feasible, it is offset
by economic disadvantage and in-
creased wastewater disposal volume.
Run B5 was carried out in the upflow
direction at 1.0 gpm, with raw water pH
adjusted to 5.5. This experimental run
provided a comparison of upflow and
downflow treatment of a regenerated
bed at pH 5.5, the same pH used in Runs
A2 and A3. A successful result could re-
duce the wastewater volume and elimi-
nate the requirement for backwashing
the bed. However, treatment capability
compared unfavorably with the down-
flow mode. The treated water arsenic
level did not reach the undetectable lev-
els common to all downflow arsenic
treatment runs; only a small amount of
0.12 H
0.10-
0.08
treated water—2,400 BV (18,000 gal)—
had levels lower than 0.010 mg/L
(Figure 3). The treated water arsenic lev-
els initially rose above the MCL after
treatment of only 8,000 BV (59,200 gal)
compared with 13,000 BV (97,800 gal)
for Run A2 and 14,800 BV (113,100 gal)
for Run A3. The results suggest that the
upflow operation is far more vulnerable
to channeling. After various methods
were attempted for restoring arsenic re-
moval capacity to a spent bed, the run
was terminated. The total arsenic re-
moved was 488 grains after 21,308 BV
(157,080 gal) were treated.
Regeneration of Treatment
Media
When the activated alumina columns
became saturated with arsenic, they
were regenerated with a 4 to 5 percent
NaOH solution. The procedure for re-
generation included upflow treatment,
then downflow treatment, raw water
rinse, and finally neutralization with
H2S04. Method A showed some reten-
tion of arsenic on the bed. A mass bal-
ance calculation gave an overall recov-
ery of 80 percent for the three Method A
regenerations. Approximately 1,996
grains of arsenic were loaded on
Column A, and three separate regenera-
tions recovered 1602 grains. However,
the results of analysis of the concen-
trated waste stream are questionable
because of high TDS in the wastewater.
No significant lowering of capacity was
noted from Run A1 to A3 (Table 3).
I
0.06
0.04-
0.02-
0.00
MCL
___
-------
Column B was regenerated in the
same manner as Column A. Total load-
ing of about 23 grains of arsenic and
recovery of 19 grains yielded a recovery
of 82 percent. The ion exchange resin
(Column C) was regenerated with 10
percent NaCI solution in the downflow
mode only. Total loading was 32.3
grains, and 17.7 grains were recovered,
producing a recovery of only 55 percent.
Handling of Waste Regenerant
The regeneration of spent arsenic sat-
urated media produced a waste product
high in dissolved solids, aluminum, and
soluble arsenic. Analysis of the waste
regeneration product from activated
alumina treatment revealed an arsenic
concentration range of 23 to 41 mg/L
and a pH of 12. EPA classifies a waste
stream with 5 mg/L or more of soluble
arsenic as a toxic waste that must be
disposed of in an approved hazardous
and toxic waste landfill.
A limited investigation was con-
ducted to treat the arsenic-laden waste
and render it nontoxic. This procedure
involved precipitation of the arsenic
with the aluminum already present in
the wastewater by adjusting the pH to 5
to 6.5, at which point the aluminum hy-
droxide precipitates out of solution. The
solids were separated from the super-
natant by mechanical dewatering. Anal-
ysis of dry solids by the EPA extraction
procedure (Federal Register, Vol. 45,
No. 98, Monday May 19,1980, Appendix
II—EP Toxicity Test Procedure) showed
that the dry cake from the centrifuge
contained 1627 mg arsenic/kg solids.
The liquid extract from the dry solids
contained only 0.036 mg/L arsenic,
which is well within the 5-mg/L limit.
Cost Estimates
Cost estimates were calculated for the
three small communities based on the
results of Method A treatment (acti-
vated alumina with raw water pH ad-
justed to 5.5). The design flows for the
three systems are 700 gpm for the NAS,
2400 gpm for the City of Fallon, and 100
gpm for the Fallon Indian Reservation.
Capital costs were estimated at
$558,000, $1,343,000, and $179,000, re-
spectively. Operation and maintenance
costs per 1000 gal treated were 22.10,
31.80, and 29.80, respectively. The high
costs for the City of Fallon were the re-
sult of the need to modify the distribu-
tion system and for high pumping costs
associated with fire prevention require-
ments.
Conclusions
Removal of the pentavalent arsenic
from the Fallon NAS drinking water was
best achieved by the activated alumina
system treating the raw water adjusted
to pH 5.5 with sulfuric acid. Fluoride re-
moval occurs along with arsenic re-
moval. Blending raw and treated water
will allow some fluoride to be present in
the product water. The waste stream
from regeneration of spent activated
alumina could be classified as toxic
since soluble arsenic is greater than 5
mg/L. However, the arsenic can be pre-
cipitated from the waste with high in-
strinsic aluminum content by lowering
the pH to 5 to 6.5. This process results in
a supernatant that is very low (<0.1
mg/L) in soluble arsenic and a solids
portion in which the arsenic is non-
leachable according to the EPA extrac-
tion procedure toxicity test. Use of
strong-base anion exchange resin was
inefficient for arsenic (+5) removal be-
cause of the competition of the high sul-
fate concentration.
The full report was submitted in fulfill-
ment of IAG AD-17-F-3-481-0 by U.S.
Department of the Navy under the spon-
sorship of the U.S. Environmental Pro-
tection Agency.
Frederick Rubel, Jr. is with Rubel and Hager, Inc.. Tucson, AZ8S711; and Steven
W. Hathaway (also the EPA Project Officer, see below) is with Water
Engineering Research Laboratory, Cincinnati, OH 45268.
The complete report.
Water at the Pallor
entitled "Pilot Study for Removal of Arsenic from Drinking
, Nevada, Naval Air Station," (Order No. PB 85-243 178/AS;
Cost: $11.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U. S. GOVERNMENT PRINTING OFFICE:1985/559-l 11/20694
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